1. Field of the Invention
The present invention relates to an apparatus for manufacturing a semiconductor device and, in particular, an apparatus for the manufacture of a semiconductor device which bonds a semiconductor element by a bonding agent on a lead frame.
2. Description of the Related Art
FIGS. 7, 8 and 9A to 9C show the steps for placing a semiconductor element on a lead frame by a conventional apparatus for manufacturing a semiconductor device.
A bonding agent coating section 10 is provided on a conveying rail 2 for conveying a lead frame 1. A dispensing unit 3 is provided on one side of the conveying rail 2. A wafer 4 having a plurality of semiconductor elements 4a is arranged on the other side of the conveying rail 2. A nozzle (11)-equipped syringe 5 is provided on the dispensing unit 3 and is movable in a direction as indicated by a first arrow 7 in FIGS. 7 and 8. A moving means mechanism 8 has its base end mounted on the dispensing unit 3 and its forward end extending toward the other side of the conveying rail 2. A pickup head 6 is mounted on the forward end of the moving means 8.
In the arrangement shown, the lead frame 1 is conveyed by a conveying rail 2 toward a direction as indicated by a second arrow 9 in FIG. 7 and is sent to the bonding agent coating section 10. Thereafter, the bonding agent 12 is applied, as a few drops, on a semiconductor element placing section of the lead frame 1 (FIG. 9A) by means of the nozzle 11 as shown in FIG. 9B.
As shown in FIG. 8, the semiconductor element 4a is sucked by a suction pad, not shown, of the pickup head 6. The pickup head 6 with the semiconductor element 4a sucked there is moved just over the dropwise-applied bonding agent 12 on the semiconductor element placing section of the lead frame 1 by rotating the moving means 8 through a given angle around the pivotal axis of the rotation shaft 8a. Then the semiconductor element 4a is pushed onto the semiconductor element placing section 1a on which the bonding agent has been dropwise applied. As shown in FIG. 9C, the semiconductor element 4a is bonded by the bonding agent to the semiconductor element placing section 1a.
Then a wire bonding step is carried out, followed by a packaging step.
Since, in the conventional apparatus, the bonding agent 12 is applied by the nozzle 11 on the semiconductor element placing section 1a of the lead frame, there occurs a variation in a thickness layer of the bonding agent applied dropwise. At that time, the bonding agent may be locally dropped as thick deposits so that, when a package is to be formed as a thinner one, the formation of such thick deposits provides a bar to the thinning of that package.
In the conventional apparatus, since the bonding agent 12 is applied as a few drops to the semiconductor element placing section 1a by means of the nozzle 11, the bonding agent 12 is not adequately distributed over the whole surface of the semiconductor element placing section, that is, less wettability occurs between the bonding agent and the semiconductor element placing section, thus producing an air layer between the semiconductor element placing section 1a and the semiconductor element 4a upon bonding them by the bonding agent. When this occurs, moisture is liable to be retained in the air layer at a reliability test such as a PCT (pressure cooker test), thus posing a reliability problem against the semiconductor device.
In the case where the bonding agent 12 is provided as an insulating layer between the semiconductor element 4a and the lead frame 1, an electric leak occurs between the semiconductor element 4a and the lead frame 1 due to the moisture in the air layer.